JPH03184677A - Method for joining metallic sintered material, pulley made of metallic sintered material and production thereof - Google Patents

Abstract

PURPOSE:To prevent the degradation in the toughness of a joined part by pressurizing and pressing the projections on the joint surface of one metallic sintered material to the joint surface of the other metallic sintered material and energizing the two members to each other. CONSTITUTION:The metallic sintered material and the other metallic sintered material or metallic material are joined. The projections 1 are, thereupon, formed on the joint surface of at least one metallic sintered material. The projections 1 are pressurized and pressed to the joint surface of the other metallic sintered material or metallic material. The two members are simultaneously energized to each other and are thereby heated without melting the projections 1, by which the two members are joined. The energization quantity between the members of the iron alloy sintered materials is specified to 1.5 to 2.6kA/mm<2> nominal current density divided by the front end area of the projections prior to welding. Problems, such as impairment of the appearance of the product by the generation of spatters, are eliminated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for joining sintered metal materials, a pulley made of sintered metal materials, and a method for manufacturing the same.

"Prior Art" Projection welding has been well known as a simple method for joining metal materials together.

This projection welding method involves forming a protrusion (projection) at the joint of one member, bringing it into pressure contact with the joint surface of the other member, and then sandwiching both members between electrodes and applying alternating current or direct current. This is a method of joining both members by applying electricity and melting the protrusion through resistance heating.

"Problems to be Solved by the Invention" By the way, when trying to apply the conventional projection welding method to joining sintered metal materials, the following problems arise.

- Gas in the pores expands due to melting of the joint, creating a blowhole within the joint, reducing joint strength. Also,
The molten metal is blown away by the pressure between the electrodes or the gas ejected from the holes, causing spatter and detracting from the aesthetic appearance of the product.

■ After melting, the joint is rapidly cooled, which significantly reduces the toughness of the joint, and the stress generated in the joint may cause cracks.

Therefore, in the past, there have been almost no examples of joining sintered materials by projection welding, and electron beam welding, which is laborious and costly, is generally used.

Therefore, in order to solve the above problem and enable projection welding of sintered materials, Japanese Patent Application Laid-Open No. 13480/1983 proposes to provide a projection on the joining surface of a pair of sintered metal materials that has a larger heat capacity. Proposals have been made to improve the above-mentioned problems by reducing the difference in heating rate at the joining surfaces of each member and making the degree of melting uniform at each joining surface.

Further, Japanese Patent Application Laid-Open No. 58-13482 discloses a method of eliminating the gas in the pores of a sintered metal material in advance by performing projection welding in a vacuum to improve the above-mentioned problem.

However, these methods are no different from conventional methods in terms of melting the joint, and although there are some improvements, spatter and blowholes are still observed, and it has been found that they do not provide a fundamental solution. .

Therefore, the present inventors conducted a detailed study on the temperature conditions of the joint surface during projection welding, which had not been given much attention in the past.As a result, the heating temperature of the joint, that is, the protrusion, was set lower than in the conventional method, and the protrusion was We have obtained new knowledge that by performing a type of diffusion bonding under conditions that do not melt, it is possible to firmly bond sintered metal materials without generating blowholes.

"Means for Solving the Problems" The present invention has been made based on the above findings, and the specific configuration thereof will be described below.

In this method, a protrusion is integrally formed on the joint surface of the sintered metal materials to be joined, and the protrusion is brought into pressure contact with the joint surface of the other sintered metal material or metal material while electricity is applied between the two members. The method is characterized in that the projections are crushed without being melted, and the bonding surfaces of both members are diffusion-bonded.

Although it is actually difficult to directly observe the state of the protrusions during bonding, it is possible to conduct experiments by increasing and decreasing the amount of current applied, and to select bonding conditions that do not show any melting traces at the bonded portion after bonding. The amount of energization can be easily set.

Note that melting here does not include localized and microscopic melting due to non-uniformity of the sintered material.

The present inventors discovered that Fe-2wt%Cu-0,7wt%C1
Fe-3wt%Ni-0,4wt%C5Fe-0,1w
Experiments were conducted on iron-based alloys such as t%C, and it was found that for this type of iron-based alloy, the nominal current density, which is the amount of current divided by the area of the tip of the protrusion before welding, is 1.5 to 2.6 KA/mm2. It has been found that sufficient bonding strength can be obtained without the protrusions (joint parts) melting and without causing problems such as blowholes and spatter. If it is less than 1.5KA/I11, the protrusion will not be completely crushed and sufficient bonding strength will not be obtained. Also, 2.
If it is larger than 6KA/xi'', the joint will melt and cause spatter or blowholes.

The current may be either alternating current or direct current, but alternating current has the advantage that bonding conditions such as the amount of current can be more precisely controlled.

Further, the energization time may be the same as that of the conventional projection method.

Note that the reason why the nominal current density is used in the present invention is that during projection bonding, the bonding area increases as the bonding progresses;
This is because the electrical resistance of the contact portion changes, making it impossible to strictly define the current density.

Therefore, in the present invention, the value obtained by dividing the amount of current by the area of the tip of the protrusion before welding is defined as the nominal current density, and the current density is limited by that value.

The pressure applied during joining may be approximately the same as that of conventional projection welding. Experiments conducted by the present inventors have confirmed that changing the pressurizing force has almost no effect on the bonding state. However, if the pressing force is extremely insufficient, electrical discharge will occur between the protrusion and the bonding surface, which is undesirable. This lower limit value is determined by the material, dimensions, etc. of the sintered material.

The size of the tip surface of the protrusion is determined by dividing the current carrying capacity of the bonding machine used for bonding by the nominal current density. Further, the position where the protrusions are formed is determined in such a way that the protrusions collapse into a drum-like shape between the joint surfaces and spread flatly in a well-balanced manner in all directions, so that good joint strength can be obtained.

The vertical cross-sectional shape of the protrusion is preferably tapered toward the distal end surface, and the Taper angle is preferably 15 to 40 degrees with respect to the perpendicular to the joint surface. If it is less than 15 degrees, the protrusions are likely to chip during pressing or handling.
If the angle exceeds 40°, the protrusion will collapse into a drum-like shape, and the current density will be insufficient in the latter half of the bonding process, making it impossible to perform good diffusion bonding.

Note that the joining surface of the sintered metal material or the metal material to be joined to this sintered metal material may be a completely flat surface, or a recessed portion may be formed at a position facing the protrusion, and the recessed portion and the protrusion may be formed. The positioning may be performed by fitting the holder with the holder.

"Example" Next, examples will be given to demonstrate the effects of the present invention.

(Example) A test piece having the shape and dimensions shown in Fig. 1 and Fig. 2 was molded with a metal sintered material of Pe-2wt%Cu-0,7wt%C.The sintered density was 6,759/ c1, the porosity was 14vo1%.The dimensions of the protrusion l were the width 1jIff
x height 1xx x length 4xx.

Next, this test piece was set in a bonding machine so as to be concentric with a sintered plate made of the same material and having an outer diameter of 30JIIX and a thickness of 33131, and the nominal DC current density was changed to 7 ways (AI-A7), and 3 Pronoe kyung yong was connected one time at a time.

As a result, when the nominal current density was less than 1.5 KA/III'', the projection I was not completely crushed, and the area of the joint IA was small as shown in Figure 5.The nominal current density was 1.5 KA/III''. In A3 to A5 of ~2.6KA/xi', the 6th
As shown in the figure, the protrusion 1 was completely crushed, a sufficient bonding area was obtained, and no melted portion was observed. In the case of 80 and A7 in which the nominal current density was further increased, as shown in FIG. 7, a melted part (diagonal part 1) was formed on the outer peripheral side of the joint, and a blowhole was formed inside the melted part. This result holds true for subsequent examples as well.

Next, the joined test piece and sintered plate were set in a tensile strength testing machine, and the tensile breaking load was measured.

Table 1 shows the average values of the above results.

(Example 2) The conditions were exactly the same as in Example I except that the sintering agent was changed to Fe-3wt%Ni-0.4wt%C, and the nominal DC current density was changed in 7 ways, and projection was performed 3 times each. Joined. The results of the same test as in Example 1 are shown in Table 2.

(Example 3) The nominal DC current density was changed in 7 ways and projection bonding was performed 3 times each under the same conditions as in Example I except that the material of the sintered material was changed to Fe-0, 1vt%C. . The results are shown in Table 3.

(Example 4) The sintered material was changed to Fe-2wt%Cu-0.7wt%C, the shape of the test piece was changed as shown in FIGS. 3 and 4, and projection bonding was performed.

Table 4 shows the results of an experiment similar to Example 1.

(Example 5) The same test piece as in Example I and melted lumber (SS 41
) was used for projection splicing. The dimensions of the ingot material are outer diameter 40 x thickness 3xx. Other conditions were the same as in Example 1. The results are shown in Table 5.

(Example 6) An attempt was made to join the pulley body 2 made of sintered material shown in FIG. 8 and the flange 3 shown in FIG. 9.

Pulley body 2 is F e -2vt%Cu-0.7wt%
It is made of C and has a cylindrical shape with a coaxial flange portion 2A integrally formed at one end, and a center hole 4 is formed in the center. The outer diameter of the flange portion 2A is l 40 xx.

The outer diameter of the belt winding portion is 128xx, and a cavity 5 for weight reduction is formed around the center hole 4. Further, on the other end surface of the pulley main body 2, six arcuate protrusions 6 are formed at equal intervals in parallel with the outer periphery, and the dimensions of these protrusions 6 are width 0.5xxx height IjIjI x length 8 shoulders. It is l. On the other hand, the flange 3 is made of molten lumber (SS41), and has a thickness of 2.5 mm, an outer diameter of 140 mm, and an inner diameter of 12 mm.

Then, as in Example 1, these were bonded with seven different amounts of current applied, and the tensile breaking load was measured by setting the pieces between jigs 7 and 8 of the tensile strength tester shown in FIG. 11.

The results are shown in Table 6. In this example as well, when the nominal current density was 1.5 to 2.6 KA/xx', no blowholes or spatters occurred, and good bonding strength was obtained.

(Example 7) Pulley body 2 made of sintered material shown in FIGS. 12 to 14
An attempt was made to join the annular flange 3 to the annular flange 3 shown in FIGS. 15 and 16.

The pulley body 2 has a cup shape made of Fe-2wt%Cu-0,7wt%C, and a center hole 4 is formed in the center thereof.
Its outer diameter is 60x1.The peripheral wall has a taper that becomes thinner toward the tip, and the thickness of the tip is 3j11. On the end face of the pulley body 2, six arc-shaped protrusions 6 are formed at equal intervals parallel to the outer periphery, and the dimensions of these protrusions 6 are 0.5 mm in width.
5xxx height lRJ+× length Byz. On the other hand, the flange 3 is made of molten lumber (SS41) and has a thickness of 2 xx, an outer diameter of 65 mm, and an inner diameter of 54 x g.

Then, in the same manner as in Example I, these were joined at seven different current amounts to obtain the pulleys shown in FIGS. 17 and 18. After that, the pulleys shown in FIG. The tensile breaking load was measured.

The results are shown in Table 7. In this example as well, when the nominal current density was 1.5 to 2.6 KA/xx'', no blowholes or spatters occurred, and good bonding strength was obtained.

(Hereinafter, blank spaces) Note that the present invention is not limited to the above-mentioned embodiments, and can be applied to other types of projection bonding, for example, as shown in FIGS. 20 and 21.

Figure 20 shows a method called edge ring projection bonding, in which sintered metal IO? , myiJ bottom part 11 is formed, and the tapered part 12A of the metal sintered material (or metal material) 12 is formed.
is applied to this opening 11, and electricity is applied to heat and bond the edge IIA of the opening It without melting it. In this case, edge IIA corresponds to the protrusion.

Also, FIG. 21 is called an interface junction, and 20
2 is a guide portion, 2 is an elongated groove, and 22 is a joining protrusion.

Then, by pressing the sintered material 12 toward the sintered material (metal material) 10 and applying electricity, the protrusion 22 is crushed and both members 10 are pressed.
12 is diffusion bonded.

Even in these types of bonding methods, the present invention can provide the same excellent effects as in the embodiments described above.

"Effects of the Invention" As explained above, according to the method for joining sintered metal materials according to the present invention, the protrusions formed on the sintered materials are diffused onto the joining surfaces of both members without melting, and the joining is performed. The gas in the pores may cause blowholes, which reduce the bonding area and reduce the bonding strength, or the molten metal may be blown away by the pressure between the electrodes or the gas ejected from the pores, causing spatter and damaging the product. There are no problems such as spoiling the aesthetic appearance of the product.

Furthermore, since the protrusions are not heated to the melting temperature, deterioration in the toughness of the joint can be prevented, and the stress generated in the joint after cooling is small, so there is no risk of cracking.

On the other hand, according to the pulley made of sintered metal material and the manufacturing method thereof according to the present invention, the pulley main body and flange, which were conventionally fixed by mechanical methods such as screws, can be joined with sufficient strength by simple projection joining. Because it can be joined with
Significant improvement in productivity and reduction in manufacturing costs can be achieved.

[Brief explanation of drawings]

1 and 2 are examples 1 to 3 of the present invention.
3 and 4 are a plan view and a sectional view taken along the line IV-ff of the test piece used in Example 5,
Figures 5 to 7 are plan views showing the quality of the joint in the test piece shown in Figure 1, Figures 8 and 9 are plan views of the pulley body and flange used in Example 6, and Figure 1O is A front view showing these joining methods, FIG. 11 is a front view showing a method for measuring the joining strength of the obtained pulley,
12 to 14 are a plan view, a vertical sectional view, and a bottom view of the pulley body used in Example 7, and FIGS. 15 and 16 are a plan view, a vertical sectional view, and a vertical sectional view showing the flange of Example 7. Figures 17 and 18 are a plan view and a vertical cross-sectional view of the pulley obtained in Example 7, Figure 19 is a vertical cross-sectional view showing a method for measuring the bonding strength for the same pulley, and Figures 20 and 21 are from this book, respectively. FIG. 7 is a vertical cross-sectional view showing another example of application of the invention. DESCRIPTION OF SYMBOLS 1... Protrusion, IA... Joint part, 2... Pulley body, 3... Flange, 4... Center hole, 5... Hole for weight reduction, 6... Protrusion, 10 ...metal sintered material, 11.
...Opening, 11A...Edge (protrusion), 12...
Sintered metal material, 20... Guide portion, 21... Relief groove,
22... Protrusion.

Claims (5)

[Claims] (1) A method for joining a sintered metal material and another sintered metal material or metal material, the method comprising forming a protrusion on the joining surface of at least one of the sintered metal materials,
The metal sintering method is characterized in that the protrusion is brought into pressure contact with the other sintered metal material or the joint surface of the metal material, and electricity is applied between the two members to heat the protrusion without melting and join the two members. How to join the binder. (2) When the metal sintered material is an iron-based alloy sintered material, the nominal current density, which is the amount of current flowing between both members divided by the tip area of the protrusion before welding, is 1.5 to 2.6 KA/mm. 2. The method for joining sintered metal materials according to claim 1, wherein: ^2. (3) Consisting of a pulley body made of a metal sintered material and a flange made of metal or metal sintered material, the flange is coaxially joined to the other end surface of the pulley body via a metal diffusion layer. Features a pulley made of sintered metal material. (4) A protrusion is formed on the end face of the pulley body made of sintered metal material, and a flange made of metal or sintered metal material is brought into pressure contact with this protrusion, and electricity is applied between both members to melt the protrusion. A method for manufacturing a pulley made of gold-sintered material, characterized in that both members are joined by heating without heat. (5) When the pulley body is made of sintered iron-based alloy material, the nominal current density calculated by dividing the amount of current between both members by the area of the tip of the protrusion before welding is 1.5 to 2.6 KA/mm^ 5. The method for manufacturing a pulley made of sintered metal material according to claim 4, wherein the pulley is made of a sintered metal material.